The output voltage is indeed adjustable via a small trim pot and does cover the claimed range. I have not tested the full output current capability yet.

In the second photo you can see where I have replaced the trim pot with a 47K (0805 size) resistor to fix the output voltage at 5.5V (to run a small red-green laser). I did this to reduce the chance of the output jumping to a higher voltage which would happen if the trim pot wiper was damaged or became intermittent. This quick mod gives me some peace of mind that the board won’t kill the attached load.

Driving one of my Christmas lasers at 5.44V output, 650mA (3.54W) the input current was 182mA with a 24V input (4.37W). That’s about 81% efficiency.

Here’s the resistor value for some other output voltages

Voltage

Resistance

2.95V

22K

3.3V

25.5K (2 x 51K in parallel, or 47K and 56K in parallel)

5V

42.7K (47K and 470K in parallel)

5.5V

47K

Unmodified boardModified for 5.5V output

A smaller version of the above board has become available. It’s a tiny 18.5mm x 11.5mm !

The next one is an older design, also from an eBay seller. It’s somewhat larger 43mm x 21mm. This one claims:

Output current: 2A (3A with heatsink)

Output voltage: 1.3V – 35V

input voltage: 4V – 40V

It uses the LM2596S-ADJ from TI (formerly National), but in reality the chips are probably fake / rebadged.

I’ve only tested the output current on this one up to about 1A, but it should be good for 2 Amps.

The adjustment on this board is via a better quality trim pot. Being multi-turn means it it much easy to adjust and should be more resistant to the set voltage drifting.

It also has a convenient mounting hole (~ 3mm) that I used to secure the board inside my Christmas laser plastic enclosure.

This board is often more expensive than the tiny one above, but the wider input voltage range and better adjustment pot are worth it for many applications.

Driving one of my Christmas lasers at 5.5V output, 760mA (4.2W) the input current was 225mA with a 24V input (5.4W). That’s about 78% efficiency.

Similar the the previous unit, this one (eBay link) has extra circuitry and adjustments for constant current (CC) operation. This one claims:

Output current: 2A (3A with heatsink)

Output voltage: 1.25V – 30V

input voltage: 7V – 35V

Testing of this board will have to wait for it to arrive early August 2014.

I’m thinking it may be useful for powering LED motifs that have had the multi-function controller (MFC) removed.

This “CHUANGRUIFA” one is labelled as 12/24V input and 5V @ 5A output. It cost me AUD $6.34 including postage via eBay.

One minor niggle was that one of the -ve wires is yellow – why not use black and save the yellow for the output +ve ?

Hooking up a resistive load of around 1.3 Ohms (4x 4.7 Ohm resistors in parallel + wiring) saw an output current of 3.75A and a voltage of 4.98V at the converter’s output wires (18.675W).

The input current was 920mA with a 24V input (22.08W). That’s about 84.58% efficiency. Despite the 3.4W loss, it was still only barely warm after a few minutes operation.

Being a potted unit, this one should survive out in the weather and even has a couple of tabs for mounting with screws or cable ties.

This converter is also labelled as 12/24V input and 5V @ 5A output. It cost me $7.04 with “free” postage via Ebay.

The wire colours make more sense on it.

Performing the same power test as above yielded the same 84.58% efficiency figure so it may use the same internal circuitry.

Having a metal case with fins should allow this converter to dissipate heat more easily. It is potted (sealed) like the other unit.